Traumatic brain injury, interpersonal violence, and postnatal mental illness: population-based study

Purpose — To examine the combined and separate impacts of traumatic brain injury (TBI) and interpersonal violence on new and severe mental illness in the postpartum period.

Methods — We undertook a population-based cohort study of 1,090,139 births in Ontario, Canada, 2012–2021. We stratified the cohort by pre-delivery history of mental health care to identify (i) new episodes of mental illness and (ii) severe mental illness within 365 days of childbirth. Modified Poisson regression was used to calculate adjusted relative risks (aRR) of these outcomes in individuals with a history of TBI and violence, TBI alone, and violence alone versus neither (referent). Then, we calculated adjusted relative excess risk due to interaction (aRERI) to quantify the super-additive risk related to the presence of both factors.

Results — The risk of any new episode of mental illness postnatally was greatest in individuals with a history of both TBI and violence (aRR 1.58; 95% CI 1.52, 1.65), followed by violence alone (aRR 1.46; 95% CI 1.42, 1.51) and TBI alone (aRR 1.24; 95% CI 1.21, 1.27), with no positive interaction between these factors. The risk of severe postpartum mental illness was greatest in individuals with TBI and violence (aRR 3.54; 95% CI 3.31, 3.78), followed by violence alone (aRR 2.50; 95% CI 2.35, 2.66) and TBI alone (aRR 1.59; 95% CI 1.48, 1.71), with evidence of positive interaction (aRERI 0.45; 95% CI 0.20, 0.70).

Conclusions — Findings show the need for tailored, trauma-informed postpartum mental health supports for individuals with histories of TBI and violence.